A MOF membrane with ultrathin ZIF-8 layer bonded on ZIF-8 in-situ embedded PSf substrate

Flexible Polypropylene-Supported ZIF-8 Membranes for Highly Efficient Propene/Propane Separation

“…Liu et al 39 reported a 4.5 μm thick ZIF-8 membrane on porous polyether sulfone (PESf) hollow fibers, which also displayed good H 2 /CO 2 separation performance after bending with curvature of ∼46 m −1 . Recently, Meng et al 40 Herein, we synthesized supported ZIF-8 layers on porous PP substrates via fast current-driven synthesis (FCDS) within 1 h. 17 The PP-supported ZIF-8 membranes show excellent C 3 H 6 /C 3 H 8 separation performance with a separation factor above 120. The most striking property of our membranes is that they can maintain their original separation performance even after bending with a big curvature of 92 m −1 , showing an excellent flexibility stability.…”

“…There are several MOF membranes successfully grown on polymer substrates. − However, considering the different mechanical properties between MOFs and polymers, polymer-supported MOF membranes have to be operated carefully to avoid any bending, otherwise the relatively fragile MOF membrane layers become damaged. − , On the basis of this, polypropylene (PP) with a smaller Young’s modulus difference from ZIF-8 is selected as the substrate to provide flexibility, thereby reducing any possible damage of the ZIF-8 membrane layer due to bending (Figure a).…”

“…To the best of our knowledge, only a few works verified the flexibility of MOF membranes grown on polymeric substrates so far. − Chen et al synthesized ZIF-8 membranes on polyvinylidene fluoride (PVDF) hollow fiber, and the H 2 /CO 2 separation performance of the membrane could be almost maintained after bending with curvature of ∼77.7 m –1 . The curvature K of a bending is the reciprocal of the radius (curvature K = 1/ r ).…”

“…Liu et al reported a 4.5 μm thick ZIF-8 membrane on porous polyether sulfone (PESf) hollow fibers, which also displayed good H 2 /CO 2 separation performance after bending with curvature of ∼46 m –1 . Recently, Meng et al prepared ZIF-8 membranes on planar polysulfone (PSf) substrates, and the CO 2 /N 2 separation performance exhibited no change after bending with a curvature of 36.3 m –1 . However, the above three MOF membranes were used for separation of small molecule gases (such as H 2 /CO 2 or CO 2 /CH 4 with kinetic diameters difference of 0.3–0.4 Å).…”

“…Nevertheless, even after bending with a curvature of 222 m –1 , the gas separation performance of the PP-supported ZIF-8 membrane can still satisfy the requirements of commercial standard (C 3 H 6 permeability > 1 Barrer and C 3 H 6 /C 3 H 8 selectivity > 35). It is known that the flexibility of ZIF-8 can be attributed to its flexible Zn–Im–Zn linkages and large void spaces. , Compared with the state-of-the-art flexible polymer-supported ZIF-8 membranes (Figure S18 and Tables S5 and S6), our PP-supported ZIF-8 membranes exhibit higher flexibility in C 3 H 6 /C 3 H 8 separation, which may due to the thinner membrane and the smaller difference of Young’s modulus between PP substrate and ZIF-8. − In addition, as shown in Figure k (inset) and Table S7, the order of their Young’s modulus is as follows: PP-supported ZIF-8 membranes > Pt-coated PP substrate > bare PP substrate. Compared with that of the bare PP substrate, the Pt-coated PP substrate and ZIF-8 membranes exhibit better mechanical property although with sacrificial tensile strength …”